1. Field of the Invention
The present invention relates to a liquid crystal display device, and more particularly, to a wide viewing angle liquid crystal display device (LCD).
2. Discussion of the Related Art
A twisted nematic liquid crystal display device (TN LCD) is a type of an LCD that is currently in wide use. TN LCDs, however, have a major drawback in that light transmittance in each grey level seen by a user depends on the viewing angle of the user. This contrast angular dependence is especially strong in the up and down direction. The angular dependence in the up and down direction is caused by the electrically induced liquid crystal director configuration.
FIG. 1 is a plan view of a unit pixel of a conventional active matrix LCD. A unit pixel is defined by data bus lines 11 and 11', and gate bus lines 15 and 15'. The data bus lines 11 and 11', and the gate bus lines 15 and 15' are respectfully arranged perpendicular to each other to form a matrix. A thin film transistor (TFT) is formed at a cross point of the data bus line 11 and the gate bus line 15 in the unit pixel. A gate electrode 13 is connected to the gate bus line 15. A source/drain electrode 12 is connected to the data bus line 11. A pixel electrode 16 is formed in the unit pixel and electrically connected to the source/drain electrode 12.
Gate and data driving circuits (not illustrated) are outside the liquid crystal panel and respectively connected to the gate bus line 15 and the data bus line 11. When the gate driving circuit applies a voltage to the gate electrode 13 through the gate bus line 15, the TFT is turned on. At the same time, an image signal applied to the data bus line 11 from the data driving circuit through the source/drain electrode 12 is applied to the pixel electrode 16.
FIG. 2 is a cross-sectional view of the unit pixel shown in FIG. 1 along the I--I' line. An insulator 3 is formed on a first substrate 1 to insulate the gate and data bus lines. On the insulator 3, the data bus line 11, a passivation layer 7, and the pixel electrode 9 are formed in sequence. A first alignment layer 17 is formed on the pixel electrode 9. On a second substrate 2, a black matrix 4 is formed to prevent a light leakage. Then, a color filter layer 5, an overcoat layer 8, and a counter electrode 19 are formed in sequence. A second alignment layer 18 corresponding to the first alignment layer 17 is formed on the counter electrode 19. An alignment direction of liquid crystal (not illustrated) in a liquid crystal layer 6 is determined by the first and second alignment layers.
The conventional LCD having the above-discussed structure aims to provide uniform alignment of liquid crystal in the unit pixel electrode by applying a uniform electric field caused by a flat pixel and the counter electrode. However, with the uniform arrangement of liquid crystal of the conventional LCD, a phase difference of light passing through the unit pixel is created according to a change in the viewing direction of the user. As a result, the viewing angle characteristics of the LCD are limited.
When the alignment layer is formed by a rubbing method, a uniform arrangement of the liquid crystal limits the viewing-angle of the LCD. Currently, researches are being actively carried out for multidomain LCDs with a light transmittance compensation in the up and down direction for improved the viewing angle characteristics. A two-domain LCD is an example of these multidomain LCDs. A method of manufacturing a two-domain LCD comprises the steps of depositing a first photoresist on a first domain of the substrate, establishing a first alignment direction by rubbing a substrate in a first fixed direction, removing the first photoresist on the first domain of the substrate, depositing a second photoresist on a second domain of the substrate and establishing a second alignment direction by rubbing the substrate in a second fixed direction different from the first fixed direction. It is also possible to manufacture a multidomain LCD with more than two domains by repeating the above process.
However, since portions of the LCD connected to the liquid crystal layer may be damaged by repeated rubbing steps during the manufacture of the multidomain LCD, the yield is decreased. Moreover, a number of manufacturing steps are necessary to create multiple domains, thereby increasing the cost of manufacturing the multidomain LCDs.